Loosely coupled Wireless Local Area Networks (WLAN) supported by WLAN servers, such as enterprise servers provide a user with such amenities as high-speed wireless Internet access and an inexpensive alternative for telephony services as well as other real-time applications. The user can carry a wireless communications unit (referred to as a communications unit) with dual-use capability so that the communications unit can provide voice communication over an enterprise server when the communications unit is in a WLAN and over a cellular wireless area network (WAN or cellular network) such as 3G when the communications unit is outside of the WLAN.
When the communications unit has a link to a first network (i.e., is on a call or is communicating over the first network) and is moving to a second network such as, for example, from a WLAN to a cellular network, it is desirable that the first network handover the link to the second network, preferably with minimal undesirable effects on the communications unit service. Since it may take a relatively long time (10s) to bring up the software and hardware necessary to operate in and register with a system, the user can experience unsatisfactory service or worse a dropped call or link. Conversely, registration with multiple systems at all times will seriously reduce battery life, so it is impractical to maintain registration with more than one network when it is not necessary.
Therefore, what is needed is a method and apparatus for providing a fast handover of a link or a connection to a communications unit between a first and a second wireless communications network without undue reduction in battery life.